The present invention particularly relates to a waterproof structure for a terminal portion of an electric wire, a cable or a wire harness provided on a housing body for electric components such as a motor case for an electric vehicle.
FIG. 4 is a sectional view showing a related waterproof structure at a through hole 2 formed with a housing body 1 for an electric apparatus such as a motor mounted on an electric vehicle, through which a terminal portion of an electric wire 4 (in this case, a shield electric wire) is inserted. The electric wire 4 is inserted through a grommet 3 formed of an elastic material such as rubber which is fitted in the through hole 2 in a watertight manner. Inside of the housing 1, an insulation sheath of the terminal portion of the electric wire 4 is peeled and an exposed conductor 4a is connected to an LA terminal (a circular plate terminal) 5 through caulking. The LA terminal 5 is fastened in a screw hole 5a with a fastening member such as a bolt. Moreover, the electric wire 4 in the outside portion of the housing 1 which does not pass through the through hole 2 is held in and fixed to a flag terminal 6 having a bracket shape. The flag terminal 6 is fastened in a screw hole 6a with a fastening member such as a bolt. Thus, the electric wire 4 is fixed to the LA terminal 5 and the flag terminal 6 in two portions of the inside and outside of the housing 1 and is straight inserted so as not to be inclined with respect to the through hole 2.
In the related electric wire terminal portion waterproof structure shown in FIG. 4, if a worker fastens the LA terminal 5 and the flag terminal 6, particularly, fastens the flag terminal 6 excessively in a direction pulling to the worker, uneven force acts on the grommet 3. As a result, the grommet 3 formed of rubber is distorted and deformed elastically so that the close contact in the through hole 2 is lost. Consequently, there is a risk that rainwater or car-washing water enters the housing 1, resulting in the damage of a watertightness function.
More specifically, when the LA terminal 5 and the flag terminal 6 are to be screwed into the screw holes 5a and 6a on the inside and outside of the through hole 2, an axis C of the screw hole 5a of the LA terminal 5 should be straight with respect to the through hole 2 by the discretion of the worker but it is actually inclined obliquely by an angle xcex81 to be an axis C1. An offset load acts around the vicinity of the grommet 3 by tensile force generated with such an inclination so that one of the sides of the grommet 3 indicated as 3a in the drawing is twisted or crushed and a clearance 7 is thereby formed between the other side indicated as 3b and the through hole 2.
Accordingly, it is an object of the invention to provide a waterproof structure for a terminal portion of an electric wire, which is able to surely maintain the watertightness of a through hole formed with a housing body for a motor mounted on an electric vehicle.
In order to achieve the above object, according to the present invention, there is provided a waterproof structure, comprising:
a housing body, formed with a through hole;
an electric wire, inserted through the through hole;
a first terminal fitting, provided with a first clamper which clamps a portion of the electric wire situated inside of the housing body to electrically connect therewith;
a second terminal fitting, provided with a second clamper which clamps a portion of the electric wire situated outside of the housing body;
a grommet, made of an elastic material and having a cylindrical shape such that the electric wire is passed through an inner periphery thereof and an outer periphery thereof is fitted into the through hole of the housing body; and
a reinforcing spacer, provided on a part of the outer periphery of the grommet so as to abut against at least one of a first edge of the through hole at an outer face of the housing body and a second edge of the through hole at an inner face of the housing body, the reinforcing spacer made of a material having greater hardness than the elastic material forming the grommet.
When the first terminal fitting and the second terminal fitting are to be screwed on the inside and outside of the housing body, both terminal fittings are fastened in such a direction that they are forcibly pulled by the discretion of a worker. In such a situation, the grommet receives an offset load in the through hole so that the grommet in a portion abutting against the edge of the through hole particularly tends to be distorted and deformed elastically. According to the above configuration, since the reinforcing spacer is provided at such a portion, the offset load can be received by the reinforcing spacer to suppress the distortion and the elastic deformation, thereby preventing a clearance from being formed together with the through hole and maintaining watertightness.
Preferably, the reinforcing spacer abuts against at least the first edge.
In this configuration, since the second terminal fitting on the outside of the housing body is easily pulled by the fastening work of the worker the elastic deformation can be prevented effectively.
Preferably, the reinforcing spacer is integrally molded with, the grommet.
In this configuration, it is possible to reduce manufacturing time and cost.
Preferably, the reinforcing spacer includes a first part having a first diameter which is substantially identical with a diameter of the through hole of the housing body and a second part having a second diameter which is larger than the first diameter. Here, the first part is fitted into the through hole and the second part abuts against either the inner face or the outer face of the housing body.
In this configuration, since the second portion abuts against the edge of the through hole to intrude thereinto, a slip is thereby eliminated to increase a degree of close contact so that the reinforcing and sealing effects can be further enhanced.
Preferably, the grommet extends so as to cover both of a part of the first clamper and a part of the second clamper.